What is zero export, and when should a factory use it?
Grid connection engineering
Zero export (also called export limitation or anti-reverse-power control) is a configuration where the PV system only supplies on-site load and never pushes power into the grid. It is a common choice for companies that want a fast self-consumption rollout without pursuing surplus export.
In this guide
01
How it works
The system measures the direction and magnitude of power at the grid connection point and instructs the inverters to reduce active power to match the load. When load drops, inverters curtail within seconds so power flow at the metering point never reverses towards the grid.
- A bidirectional meter or current transformers at the connection point or main incomer.
- A controller (logger/EMS) computing the allowed power and dispatching setpoints to the inverters.
- Inverters that support external active power limitation commands.
- A small positive safety threshold so sudden load drops do not cause momentary export.
02
Advantages and the trade-off
- Pro: simpler paperwork and grid connection agreement because nothing is sold to the grid.
- Pro: avoids export metering disputes and curtailment exposure.
- Con: some yield is lost during low-load hours, weekends and holidays (export clipping).
- Con: extra metering and control hardware, and the logic must be re-verified whenever load configuration changes.
How much yield is lost depends on the load shape: negligible for a plant running three shifts, potentially significant for an office closed at weekends.
03
Zero export or registering surplus export?
Under Decree 58/2025/ND-CP, grid-connected self-consumption rooftop solar may sell surplus energy within the prescribed limits. Choosing zero export is therefore an economic and administrative decision, not a technical requirement.
- Choose zero export when daytime load is large and stable and you want a fast, simple rollout.
- Register surplus export when load fluctuates strongly and the surplus is large enough to justify the extra process and metering.
- Add BESS when you want to capture the energy that would otherwise be curtailed for evening or weekend use.
- For multiple workshops behind one connection point, re-simulate the export limit for the whole cluster.
04
Testing and commissioning a zero export system
- Perform sudden load-shedding tests to measure response time and momentary export.
- Log power at the connection point continuously for at least a week covering all operating modes.
- Verify behaviour when communication between controller and inverters is lost (it must fail safe).
- Keep the threshold configuration and test records for commissioning and future audits.
Frequently asked questions
Does zero export shorten inverter life?
Power limitation is a standard, manufacturer-supported operating mode and does not damage inverters; what matters is sensor quality, communication reliability and sensible thresholds so the inverter is not constantly hunting.
How much yield is lost with zero export?
It depends on the load curve and on installed capacity relative to daytime load; the correct way to quantify it is to simulate yield against the plant's actual 15-minute load data rather than assuming a generic percentage.
Can we remove zero export later to sell surplus?
Yes, but it requires the corresponding process and connection agreement with the utility, export metering per regulation, and a review of protection settings before the export limit is raised.
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Sources
- Decree 58/2025/ND-CP on renewable energy development – Vietnam national legal database
- Vietnam Electricity (EVN)
- IEC – International Electrotechnical Commission
This guide compiles reference information from legal documents and official sources; it is not legal advice. Technical and financial ranges are industry reference values — project decisions require a site-specific survey.
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